Sulphur recovery



Aug. 31, 1937. F. M. NELSON SULPHUR RECOVERY Filed Oct. 18, 1934 2 Sheets-Sheet 1 NM R V v 0. .WE T m W m -m T R F. M. NELSON SULPHUR REcoVsRY Filed Oct. 18, 1934 Aug. 31, 1937.

2 Sheets-Sheet 2 INVENTOR FRED M- NELSON ATTORNEYS Patented Aug. 31 1937 UNITED STATES SULPHUR RECOVERY Fred M. Nelson, Newgulf, Tex., assignor to Texas Gulf Sulphur Company, a corporation of Texas Application October 18, 1934, Serial No. 748,792

5 Claims.

This invention .relates to the recovery of sulphur and has for its object the ,provision of an improved method and apparatus for recovering sulphur from underground deposits of elemental sulphur.

In the recovery of sulphur from deposits disposed beneath the surface of the earth, the socalled underground fusion or Frasch process is generally employed. In accordance with this process as it has heretofore been practised, a hole or well is drilled through the strata overlying the sulphur formation and is cased. A smaller hole is drilled below this casing to extend the well to a suitable depth into the sulphur formation. A system of co-axially arranged conduits is set through the casing and the smaller hole extending therebelow to the bottom of the well to provide a series of annularconduits communicating with the sulphur deposit and the surface of the ground. Through at least one of these annular conduits, generally the outermost, superheated water is introduced into the deposit, where it contacts and melts the sulphur. The melted sulphur collects in a body at the base of the well, where it enters the lower portion of another of the annular conduits, hereinafter referred to as the sulphur discharge conduit.

Air is introduced into the body of molten sulphur in the lower portion of the sulphur discharge conduit through one of the co-axial conduits, generally the innermost, to produce a mixture of sulphur and air having an average density sufficiently low so that the pressure exerted by the superheated water upon the body of molten sulphur'will raise it to the surface of the ground, in accordance with the familiar principle of the air lift. Enough air is introduced so that the sulphur will not only be raised or pumped substantially to the level of the ground, but will be forced through suitable conduits to a reservoir, or to the top ofa vat, where it may solidify.

When substantially all of the melted sulphur has been discharged from the well, the sulphur discharge conduit, in addition to .the outer annular conduits, is employed to introduce superheated water into the well to melt a further quantity of sulphur.

Operation of this process in the manner described above has been found to be accompanied by a number of disadvantages. For example, when liquid melted sulphur, under pressure and at high temperatures, is mixed with air, water, steam and other substances such as are commonly found in sulphur deposits, acids of an excool and tremely corrosive nature, such as sulphuric acid,

7 are formed. These acids attack and may destroy the sulphur discharge conduit in the well, the conduits through which the sulphur is carried from the well to the reservoir or to the vat, and 5 other metal parts with which they come in con-' tact.

Furthermore, when operating in the above described manner, steam and air separate from the sulphur in the conduits leading to the reservoir 10 or vat, causing hammers which not only subject the pipe lineto severe physical strain, but which also rupture any surface-protecting coating which has formed on the walls of the conduit,

with the result that fresh surfaces of metal are exposed to the attack of the corrosive substances present in the sulphur.

The mixture of sulphur with air, water, steam, gas and fumes, together with other substances present in the sulphur as it is discharged from the well, has a volume several times greater than that of the sulphur itself; Consequently, larger conduits must be provided to transport the mixture, and a greater pressure is required to force it through the conduits, than would be required to handle the sulphur alone. Furthermore, since the pressure which can be applied to the body of molten sulphur at the base of the well is limited by the porosity of the formation in-which the sulphur deposit occurs, it is necessary to increase the amount of air employed in the air lift, and thus still further to increase the volume of the sulphur-air mixture, if the mixture is to be pumped for any considerable distance. The importance of these considerations becomes apparent when it is realized that the reservoir or vat to which the sulphur is pumped may be at a distance up to several miles from the well.

Another important disadvantage to the abovedescribed process as it is generally practised is owing to the fact that the sulphur in the deposit contains a varying amount of impurities comprising oils and other carbonaceous materials. When the sulphur is meltai, these oils and other carbonaceous materials begin to discolorize it. The longer the sulphur is held in the molten state, the darker it becomes, even when the amount of oils and other carbonaceous materials is very small. If the superheated water which is introduced into the deposit melts the sulphur faster than it can be pumped from the well, this discolorization may assume serious proportions, for in such a case the melted sulphur accumulating at the base of the well becomes dark, and it in turn darkens all of the sulphur produced by the well.

In accordance with the present invention, it is possible to overcome the foregoing disadvantages to the underground fusion process for the recovery of sulphur by separating from the sulphur as it emerges from the'well those substances which are admixed therewith and which have densities less than that of the melted sulphur itself. The

separation of these substances, comprising chiefly air, water and steam, from the melted sulphur greatly reduces the volume of material which must be handled beyond the well-head, with the result that smaller conduits may be employed to transport the sulphur to the reservoir or vat, and less air is required in the air lift to provide for the pumping of the sulphur. Furthermore, it is possible to increase the capacity of the air lift pump, and, therefore, to decrease the length of time during which molten sulphur is maintained incontact with the oils and other carbonaceous impurities of the deposit, with the result that a sulphur product of high purity and bright color may be obtained. In addition, the productive capacity of the well may be increased, and the life of the equipment employed may be prolonged.

The separation of the air, water and steam from the molten sulphur is brought about in a separating chamber located between the reservoir or vat and the well-head and preferably near the well-head. The molten sulphur from the well, together with the substances admixed therewith,

is introduced into the separating chamber, wherein the melted sulphur settles to the bottom and the air, water and steam rise to the top and are withdrawn. The pressure exerted by the substances introduced into the separating chamber is utilized to force the moltensulphur from the collecting chamber to a reservoir or vat, in

which it may be allowed to cool and solidify.

Other substances than air, water and steam which have densities less than that of melted sulphur and which are admixed therewith when it is introduced into the separating chamber,

5 may also be separated from the melted sulphur.

Air, water and steam comprise the chief substances separated, however, and particular reference will be made to them, but it will be understood that in the specification and in the ap- 50 pended claims the words "air, water and steam are intended to include all substances having densities less than that of the melted sulphur which are admixed therewith a it is discharged from the well and which separate therefrom in 55 the separating chamber.

The invention will be better understood from the following description, taken in connection with the accompanying drawings, in which Fig. 1 is an elevation, partly in section, of an so apparatus adapted for the practice of and embodying the invention; and

Figs. 2 toe, inclusive, show apparatus of the type illustrated in Fig. 1 provided with modified valve arrangements.

The apparatus shown in Fig. 1 of the drawings comprises a vertically disposed separating chamber i0 having an inlet conduit il through which molten sulphur and substances admixed therewith may be introduced from the sulphur well 70 into the separating chamber. The inlet conduit II is preferably an extension of the sulphur discharge conduit leading from the bottom of the well. A short conduit i2 and an outlet conduit I3 provide for the removal of molten sulphur 75 from the lower portion of the separating chamher to a reservoir or vat for sulphur (not shown).

The entire separating chamber is surrounded by a steam jacket I, into which steam from a suitable source may be introduced through conduits l5 and i6. The conduit 15 preferably extends through the outlet conduit l3 substantially in axial alignment therewith to a point adjacent the reservoir or vat. The conduit i 5 emerges from the interior of the sulphur conduit i3 through a packing gland l'l.

Conduits l8 and 20 provide for the escape of steam from the steam jacket I4 and for introducing it into a conduit 2|, which passes through a packing gland 22 and the separating chamber Ill into the inlet conduit II. The conduit 2lextends through the inlet conduit in substantially axial alignment therewith to some convenient point, for example, to the well-head. Steam passing through the conduits l5 and i6, the steam jacket, and the conduits i8, 20 and 2| in the direction indicated by the arrows serves to maintain sulphur passing through the outlet conduit i3, the separating chamber i0, and the inlet conduit ii in the molten state.

An orifice 23 in the upper portion of the separating chamber it) provides for the escape of the air, water and steam which separates from the sulphur in the separating chamber. A conduit 24 communicating with a chamber 25 above the orifice 23 permits withdrawal of the mixture of air, water and steam which passes through the orifice.

In the valve structure shown in Fig. 1-, a needle valve 26 operated by a float 21 is employed to close the orifice 23. Surmounting the fioat and firmly attached thereto is a holder 28 provided with transverse bars or plates 30. A stem 3i, supporting upon its upper end portion the needle valve 26 and carrying upon its lower end portion a button 32, is positioned within the holder and extends through holes in the transverse bars 30 thereof. The length of the stem 3i between the needle valve and the button is somewhat greater than the distance between the transverse bars or plates, and it is therefore possible for the stem 3i to slide axially back and forth through the holes. Preferably the diameter of the holes is a trifle greater than the diameter of the stem 3!, so that the stem and needle valve 26 may move transversely to a slight extent to insure proper seating of the valve when it is raised by the float to the closed position. The button 32, the diameter of which is greater than that of the holes, prevents the accidental withdrawal of the stem from the holder. 1

A plug 33, through which the orifice 23 extends, is detachably mounted in a supporting plate 34. The supporting plate is in turn detachably mounted on a closure plate 35, and the whole assembly is adapted to engage with an end plate 36 to close the upper portion of the separating chamber II.

'A removable cap 31 serves to close the chamber 25 above the orifice. By removing the cap, access may be had to the orifice assembly and the valve for repairs or replacements.

A sleeve 33, the upper portion of which is perforated, extends downwardly from the closure plate 35 and surrounds the upper portion of the holder 23 to provide a guide therefor. A perforated cylinder 33 extends downwardly from the end 9,091,829 m the modified valve structures shown in Figs.

2 to 4, the orifice 25 extends through a plug' 42 which engages with an-end plate 42 of the sepa-- rating chamber II. A stem 44 passes throughthe 5 orifice and supports on either side thereof valves 45 and 45 adapted 'to seat in the plug 42 and thereby to close the orifice. The upper portion of the stem 44 extends to a point above the uppermost valve 45. The length of the stem between the valves 45 and 45 is greater than the length of the orifice, so that axial movement of the stem through the orifice is possible and so that not more than one valve may be closed at a time. The diameter of the stem is substantially less than the diameter of the orifice so that when' the stem is in a mid-position and both valves are open, air, water and steam may escape through the annular passage between the orifice walls and the stem.

The chamber ab'ove'the orifice is closed by a removable cap 41. The upper portion of the stem 44 extends through the chamber 25 and through a packing gland 45 in the cap 41.

Means operatively associated with the upper 25 portion of the stem 44 provide for axial movement thereof so that the valves 45 and 45'may be opened and closed. In the apparatus shown in Fig. 2, these means comprise a compression spring 50 engaging the upper surface of the packing gland 42 and the under surface of a washer 5| which is firmly attached to the stem. The spring tends to lift the stem and to hold the lowermost valve 45 in a closed position against its seat in. the plug 42.

The upper end portion of the stem extends through a solenoid 52 which is electrically connected to a source of current and which may be controlled by a rheostat 52 or in any other suitable manner. The uppermost end portion of the whereas the stem below this portion 'is nonmagnetic. when no current is passing through the solenoid, the stem is lifted by the spring 55 and the non-magnetic portion of the stem is held so that it extends-substantially into the solenoid, with the magnetic portion of the stem extending thereabove. a

When current is passed through the solenoid, the magnetic portion of the stem is drawn downwardly into the solenoid against the action of the spring 55, whereby the lower valve is opened and the upper valve 45 is forced into a closed position against its seat in the plug 42. By controlling the current passing through the solenoid, it is possible to control the pressure with which the upper valve 45 is held closed.

In the modified valve structure shown in Fig.-

3, the valves 45 and 45 are operated by means of fluid pressure applied above a diaphragm 55. The upper end portion of the stem 44 is attached to the diaphragm substantially at its center, and

the diaphragm, when no fluid pressure is applied thereabove, exerts an upward force on the stem plug 42.

when fiuid ,pressure is applied above the stem adjacent the upper portion of the solenoidto hold the lower valve 45 against its seat in the Fig. 4, scompression spring 45 engages the upper surface of the packing gland 42 and the .under surface of a washer II which is firmly attached to the stem 44. The springexerts an upward force on the stem and tends thereby to hold the lower valve 45 in a closed position against the plug 42.

A lever 42 is pivoted adjacent one'end to asupporting member 52. A hinge member 54 engages the upper end portion' of the stem 44 above.

the washer 5i, and the lever is pivoted thereto at its fulcrum. A weight 55 is mounted upon the outer portion of the lever beyond its fulcrum at the hinge member 54, and is adapted to slide thereupon.

when the weight is moved to the outer end portion ofthe lever away from its fulcrum, the lever forces the stem 44 down against the pressure exerted by the spring until the upper valve 45 engages its seat in the plug 42. By regulating the distance of the weight from the fulcrum' of the lever at the hinge member 54, it is possible to control the force with which the upper valve 45 is held in a closed position.

'. The operation of the apparatus shown in Fig.

1 is as follows: Molten sulphur. from the well, together with the air, water and steam admixed therewith, is pumped into the separating chamber l0 through the inlet conduit II. The molten sulphur settles to the bottom of the separating chamber and the air, water and steam, which have densities substantially less than that of the molten sulphur, rise to the surface thereof. The molten sulphur enters the short conduit l2 and the outlet conduit l2, whilethe air water and steam pass through perforations in the cylinder 35 and the sleeve 25 and through the orifice 22 into the chamber 25. From the chamber 25 these substances are withdrawn through the conduit 24 to suitable collecting tanks (not shown), or they may be discharged into the atmosphere.

Generally,.the molten sulphur will be pumped into the separating chamber more rapidly than the static pressure therein can force it through the outlet conduit i2. Consequently, a body of molten sulphur accumulates within the separating chamber until it attains a depth at which the float 21 and the needle valve 25 operated thereby begin to rise. As molten sulphur'continues to accumulatewithin the separating chamber, the float and needle valve are lifted until the orifice 22 is closed. Further introduction of. molten sulphur, air, water and steam into the separating chamber increases the pressure therein, with the result that the molten sulphur is forced through the conduits I2 and If to the reservoir or vat.

During this phase of the operation, the level of the sulphur within the separating chamber,

- and with it the float 21, is lowered. The needle .the separating chamber,- 'and thev needle valvedrops-back to its original position in relation to the float. The entire operation is repeated as molten sulphur continues to enter the separating chamber.

When substantially all of the melted sulphur has been pumped from the well, it is expedient to introduce superheated water into the deposit through the sulphur discharge conduit in the 5 well. This is accomplished by admitting water under pressure to the outlet conduit ll. The water flows therethrough to the separating chamber, in which it rises until the float and needle valve are lifted sufliciently to close the orifice.

The water then flows through the inlet conduit ii to the sulphur discharge conduit and thence to the sulphur deposit. When a suillcient quantity of sulphur has been melted in the well, ,the supply of superheated water to the outlet conduit i3 is shut on and pumping operations are resumed.

The operation of the various modifications shown in Figs. 2-4 is substantially the same as the operation of the apparatus illustrated in Fig.

1, differing therefrom only in so far as is required by the different valve construction.

During the pumping operations, a downward force is applied to the stern N by electromagnetic action, fluid pressure or the lever and weight mechanism, substantially as described above, to hold the upper valve 45 in its closed position against the plug 44. Sulphur, admixed with air, water and steam, enters the separating chamber l0 through the inlet conduit ii. The sulphur settles to the bottom of the chamber. and the air, water and steam, owing to their lower densities, collect above it. As the sulphur continues to enter the separating chamber, the pressure therein is increased and the sulphur at the bottom of the chamber is forced through the short conduit l2 and the outlet conduit ii to the reservoir or vat;

When substantially all of the sulphur in the separating chamber has thus been forced out, a

mixture of sulphur with air, water and steam enters the conduits I2 and i3. Because a greater pressure is required to force this mixture through i the conduits than is required for sulphur alone, a greater pressure begins to develop within the separating chamber. This greater pressure is suflicient to overcome the downward pressure holding the upper valve 45 closed, and it is accordingly forced open, allowing the air, water and steam to escape through the orifice to the .50 chamber 25, whence they are withdrawn through the conduit 24. When enough air, water and steam have escaped from the separating chamber to reduce the pressure therein to a value below that required to hold the valve 45 opened, it is again closed and the operation is repeated.

When substantially all of the melted sulphurhas been pumped from the well, superheated water may be introduced into the sulphur deposit through the sulphur discharge conduit. This is accomplished by releasing the force acting downwardly on the stem 44 and allowing-it to be lifted by the spring or the diaphragm, substantialiy as described, to close the lower valve 46. Thereupon, superheated water may be admitted 5 to the outlet conduit i3, through which it flows to the separating chamber. From the separating chamber it passes through the inlet conduit ii and the sulphur discharge pipe to the sulphur deposit. when suflicient sulphur has been melted, the pumping is resumed and the cycle of operations is repeated.

The use of the invention permits 01' marked economy in the amount of air consumed in pumping sulphur. As an example of the efllciency of the invention, the following data relating to the operation of a sulphur well located about 2000 feet from the reservoir are presented:

Other economies may also be eifected by the use of the invention. For example, it is possible to reduce the size of the conduits leading to the sulphur reservoir, and the life 01' these conduits is prolonged by reducing the quantity of corrosive materials in the sulphur transported through them. By increasing the rate at which the sulphur may be pumped from the well, use of the invention increases the productive capacity thereof and results in the production of sulphur of a higher degree of unity and of a brighter color than could otherwise be produced.

I claim:

1. In a process for recovering sulphur from an underground deposit which involves introducing superheated water or steam into the deposit to produce a mixture comprising molten sulphur, air and water, the improvement which comprises introducing the mixture under pressure into a separating chamber substantially immediately upon its emergence from underground, separating the molten sulphur from the air and water in the separating chamber, separately withdrawing the molten sulphur and the air and water from the chamber, and controlling the rate at which air and water are withdrawn from the separating chamber to maintain therein adequate pressure for forcing the molten sulphur from the separating chamber and through a conduit.

2. In a process for recovering molten sulphur from an underground deposit which involves producing, a mixture of molten sulphur with substances of lesser densities than molten sulphur,

the improvement which comprises introducing said mixture under pressure into a separating chamber substantially immediately upon emergence of the mixture from underground, separating the molten sulphur from the substances of lesser densities in the separating chamber, separately withdrawing the molten sulphur and the separated substances from the separating chamher, and controlling the rate at which said separated substances are withdrawn from the separating chamber to maintain therein adequate pressure for forcing the molten sulphur from the separating chamber and through a conduit.

3. In a process for recovering sulphur from an underground deposit which involves introducing superheated water or steam into the deposit to produce a mixture comprising molten sulphur, air and water, the improvement which comprises introducing the mixture as it 'is discharged from the well under pressure into a separating chamber, maintaining the mixture in the separating chamber under superatmospheric pressure, separating the molten sulphur from the air and water in the separating chamber, separately withdrawing the molten sulphur and the air and water from the chamber, and maintaining adequate pressure in the separating chamber to force the molten sulphur from the separating chamber through a conduit by controlling the rate at.

which air. and water are withdrawn from the separating chamber. 4. In a process for recovering sulphur fro an underground deposit which involves introducing superheated water or steam'into the deposit under pressure to produce a mixture comprising molten sulphur, air and water and elevating said mixture to the surface of the earth by the pressure exerted by the introduced superheated water or steam, the improvement which comprises introducing the mixture discharged from the well into a separating chamber, maintaining said mixture in the separating chamber under superatmospheric pressure due to the pressure of the superheated water or steam introduced into the deposit to produce said mixture and to elevate it to the surface of the earth, permitting the heavier molten sulphur of the mixture to settle to the bottom of the separating chamber, forcing said molten sulphur from the bottom of separating chamber through a-conduit by means of the super-atmospheric pressure maintained in said separating chamber, and separately withdrawing separated air and water from the separating chamber.

5. In a process for recovering sulphur from an underground deposit which involves introducing superheated water or steam into the deposit under pressure to produce a mixture comprising molten sulphur, air and water and elevating said mixture to the surface of the earth by the pressure exerted by the introduced superheated water or steam, the improvement which comprises introducing the mixture discharged from the well into a separating chamber, maintaining said mixture in the separating chamber under super-atmospheric pressure due to the pressure of the superheated water or steam introduced into the deposit to produce said mixture and to elevate it to the surface of the earth, permitting the heavier molten sulphur of the mixture to settle to the bottom of the separating chamber, forcing said molten sulphur from the bottom of separating chamber through a conduit by means of the super-atmospheric pressure maintained in said separating chamber, and controlling the pressure in said separating chamber by controlling the rate at which air and water are withdrawn from said separating chamber.

FRED M. NELSON. 

